* In all spectra, a peak at around 420 nm is visible. Based on spectra of porphine in the salt solutions alone, it is likely that this peak is due to the presence of porphine in the films. The peak absorbance at 420 had the highest value for films soaked in 10 mM Na<sub>2</sub>SO<sub>4</sub>, while the peak absorbance was the lowest for films soaked in Al<sub>2</sub>(SO<sub>4</sub>)<sub>3</sub>. This corresponds to the fact that all films soaked in the latter solution remained green in color and did not become pink, even after soaking for several hours.

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In all spectra, a peak at around 420 nm is visible. Based on spectra of porphine in the salt solutions alone, it is likely that this peak is due to the presence of porphine in the films. The peak absorbance at 420 had the highest value for films soaked in 10 mM Na2SO4, while the peak absorbance was the lowest for films soaked in Al2(SO4)3. This corresponds to the fact that all films soaked in the latter solution remained green in color and did not become pink, even after soaking for several hours.